Question:

A boy has five blue marbles, four green marbles and three red marbles. In how many ways can be arrange four of them in a row, if the marbles of any one colour are indistinguishable?

The if blue 1...... blue 5 are all indistinguishable this is the same for green and red

thus the answer would be $\displaystyle \frac{12!}{5!4!3!} = 27720 $ but the answer is 80 in the book where did i go wrong?